inches, placed over the mouth and nostrils, and kept in position by elastic bands passed round the ears. The pad should be burnt after use. With a smooth, impervious floor, however, and ventilation designed to remove the fumes and dust at, or as near as possible to, the point of origin, lead poisoning would become very rare in most of the industries to be described. The essential points of such a system are--(1) The draught or current of air set in motion either by heat or by a fan; (2) the ducts along which the current travels; (3) the hoods or air-guides designed to intercept and catch the fumes and dust at the point of generation; (4) inlets from the outside air into the room to replace continuously the air extracted, and, in many cases, (5) a suitable dust filter or collector. _Exhaust by Heat._--Processes giving rise to fumes or to dust liberated on stirring or skimming, which can be dealt with by the draught created in the furnace flue or over a bath of molten metal provided with adequate hood and duct up which the heated air travels, are--Smelting, refining, spelter manufacture, and the numerous operations necessitating the melting of lead, such as tinning with a mixture of tin and lead, sheet lead and lead piping, stereo pots in letterpress printing, pattern-making, tempering springs, file-hardening, etc. The dusting of red-hot metallic surfaces, as in vitreous enamelling, might possibly also be dealt with in the same way. The disadvantage of the exhaust by heat is the uncertainty and inequality of the draught, and the size of the duct necessary to cope with the volume of rarefied air from above the molten vessel. The closer the hood is brought down over the point where the fumes escape, the less risk is there of cross-currents deflecting them into the workroom. Hence all baths of molten metal should have the sides and back closed in, leaving as small a space open in front as is practicable in view of necessary skimming or other operations.